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DTC codes / P0Axx · Hybrid propulsion / P0AF3

P0AF3Drive Motor Inverter Temperature Sensor B Circuit Range/Performance

P0AF3 indicates that the drive motor inverter temperature sensor B circuit has reported a range or performance fault, meaning the voltage signal from that sensor is outside the expected operating window or is not changing in a plausible way as the inverter warms and cools. The computer compares the sensor's output against modeled temperature and other sensor readings, and it sets this code when the signal is stuck, erratic, or out of bounds.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the check engine light or a dedicated hybrid/EV warning lamp, often with no other symptoms.
  • Reduced power output or a limp-home mode if the inverter control strategy derates the drive motor to protect the electronics.
  • Intermittent loss of propulsion or a sudden shutdown while driving, particularly under high load or during repeated acceleration.
  • A message on the driver information display indicating a hybrid or electric drivetrain fault, sometimes accompanied by a chime.
  • Overheating warnings for the inverter or drive motor if the sensor fault masks a genuine thermal problem.
  • Often no symptoms besides the warning light, because the sensor circuit fault may not immediately affect drivability.

Common causes, most likely first

  1. A faulty inverter temperature sensor B itself, with an open, shorted, or drifted thermistor element inside the inverter assembly.
  2. Damaged, chafed, or corroded wiring in the sensor circuit between the inverter and the control module, often from heat cycling or road debris.
  3. A loose or contaminated connector at the inverter or at the control module, causing intermittent high resistance.
  4. A failing control module that misinterprets the sensor signal or has an internal driver fault on the sensor circuit.
  5. Coolant flow problems or a failing inverter cooling pump that cause real temperature excursions the sensor correctly reports but the model flags as out of range.
  6. Software or calibration issues in the inverter control module that set a false range fault under specific operating conditions.
  7. Aftermarket accessories or improper repairs that introduce electrical noise or incorrect resistance into the sensor circuit.

How to diagnose and fix it

  1. Connect a scan tool and record the freeze-frame data for P0AF3, then clear the code and verify whether it returns immediately or only after a specific drive cycle.
  2. Inspect the inverter temperature sensor B connector and harness for corrosion, pushed pins, chafing, and heat damage, and repair any obvious wiring faults.
  3. Measure the sensor resistance with a multimeter at the sensor connector and compare it to the manufacturer's temperature-resistance chart, checking for opens, shorts, or a value that does not change with temperature.
  4. Back-probe the sensor signal circuit at the control module and compare the voltage to the sensor's actual resistance to isolate whether the fault is in the wiring or the module.
  5. Verify inverter coolant level, coolant flow, and cooling pump operation, because a genuine overheating condition can trigger a range fault in the temperature model.
  6. If the sensor is internal to the inverter and not serviceable separately, follow the manufacturer's procedure for inverter replacement or internal sensor repair.
  7. After repair, clear codes and run the manufacturer's specific drive cycle to confirm the monitor completes and the code does not reset.

What the inverter temperature model hides

  • Many technicians replace the inverter assembly when the real fault is a chafed wire in the harness near the inverter, so always perform a resistance and voltage-drop test on the circuit before condemning the unit.
  • A P0AF3 can be set by a cooling system fault rather than an electrical sensor fault, because the control module compares the sensor signal to a thermal model and flags a range error when the actual temperature deviates from expected.
  • The sensor B circuit may share a reference voltage or ground with other sensors, so a fault in a neighboring circuit can corrupt the temperature reading and set this code without any problem in the sensor itself.
  • Intermittent codes that appear only after a long drive or under high load often point to a connector that opens when hot, so wiggle-test the harness while watching live temperature data.
  • Some vehicles require a relearn or adaptation reset after inverter or sensor replacement, and skipping that step can cause the code to return even though the repair was correct.

Can I keep driving with P0AF3?

You can generally drive the vehicle to a service location if the only symptom is a warning light and power output feels normal, but avoid heavy acceleration, sustained high speeds, and towing until the fault is diagnosed. If the vehicle enters limp mode, shows an overheating warning, or loses propulsion, stop safely and have it towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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